Die casting is a popular method of forming articles of manufacture from zinc and magnesium alloys, especially for thin walled parts. Zinc and magnesium have relatively low melting points and are suited to both hot chamber die casting and cold chamber die casting. In hot chamber die casting, molten zinc or magnesium is pushed from a crucible, or pot, into a die casting system through a nozzle. The molten metal enters the die casting system through a sprue where it then travels through a runner system before entering the die cavity of a mold. The molten metal flows into the die cavity, where it solidifies and forms an article having a shape matching the die cavity. The solidified articles are then ejected from the mold, so that the process can be repeated. It is advantageous to cycle the molten metal through the runners and die cavity and then cool it down as fast as possible to keep cycle times down, and in turn keep production time and costs down.
One way to keep cycle times down is to control the temperature of the molten metal so that it enters the die at the optimal temperature to allow it to both flow through the runner system rapidly and cool rapidly. Temperature controlled sprue systems are commonly used to control the temperature and volume of molten metal that enters the runner system and the mold. In a temperature controlled sprue system, cooling fluid, such as water, is circulated through the inside of the die and around the sprue in order to remove heat from the die casting system that has been absorbed from the molten metal at the desired time, rate and location.
In these types of systems, a runner cooling block in which the sprue is located contains a system of channels for circulating cooling fluids through the runner cooling block very near where the molten metal enters the die at the sprue. This allows for control of the temperature of the molten metal as it enters the die casting system. When cooling fluid is circulated through the runner cooling block, heat from the molten metal is absorbed by the runner cooling block and dissipated by the cooling water. This reduces the time required to solidify the molten metal in the die cavity and the runner system, which in turn keeps cycle times down. However, conventional runner cooling blocks only provide limited levels of thermal dissipation. As such, there is a need for runner cooling blocks with improved thermal dissipation and heat transfer characteristics to reduce cycle times in die casting systems.